1. Field of the Invention
The present invention relates to a converter for satellite broadcast or communication reception to receive a circularly polarized wave comprising a vertically polarized wave and a horizontally polarized wave.
2. Description of the Prior Art
A conventional converter for satellite broadcast reception will be described below with reference to FIGS. 13 to 16, of which FIG. 13 is a perspective view of the conventional converter for satellite broadcast reception, FIG. 14 is a sectional view taken on line 14xe2x80x9414 in FIG. 13, FIG. 15 is an enlarged view of a principal portion, explaining a mounted state of a probe, and FIG. 16 is an enlarged view of a principal portion, showing a mounted state of a circuit board.
As best seen in FIGS. 13-14, a housing 31 and a waveguide 32 are formed integrally using a metallic material such as die-cast aluminum or zinc. The housing 31, which is formed in a generally rectangular box shape, comprises a bottom wall 31a, side walls 31b formed upright so as to enclose the bottom wall 31a while allowing an upper side to be open, a receptacle portion 31c enclosed with the side walls 31b, a vertical through hole 31d (see FIG. 15) formed in a position close to one end portion of the bottom wall 31a, and stepped portions 31e formed by cutting out peripheral edges of upper ends of the side walls 31b. The waveguide 32 is formed in a cylindrical shape relatively small in diameter and is projected from the bottom wall 31a at the position of the through hole 31d. The waveguide 32 comprises a generally cylindrical portion 32b having an opening 32a for introducing a polarized wave, a hollow portion 32c formed centrally in the longitudinal direction of the cylindrical portion, and a holding portion 32d formed as a semi-cylindrical recess within the cylindrical portion 32b, the holding portion 32d extending toward the opening 32a from a peripheral edge position of the through hole 31d formed in the housing 31, as shown in FIG. 15.
As best seen in FIG. 15, a probe 33 for catching a horizontally polarized wave is made up of a cylindrical insulating portion 33a formed of, for example, a fluorine resin, polyethylene, or Teflon, and a linear central conductor 33b piercing through the center of the insulating portion 33a and formed of a metal such as brass or nickel. The central conductor 33b has one end portion 33c which is bent approximately at right angles and an opposite end portion 33d which is rectilinear.
As shown in FIG. 16, a single rectangular circuit board 34 formed by an insulating board comprises a thin flat plate portion 34a, three vertical through holes 34b formed near a side edge of the flat plate portion 34a, bridge portions 34d and 34e which are formed in T shape, and a small hole 34c formed near the through hole 34b. A copper-clad earth conductor 35 is formed on a lower surface of the circuit board 34 except the lower surface portion where the bridge portion 34e is formed. A lower surface of the bridge portion 34d functions as a short-circuit rod for the probe 33.
A probe 36 for catching a vertically polarized wave is formed as a conductive pattern on an upper surface of the flat plate portion, extending from an intersecting point of the bridge portions 34d and 34e toward the flat plate portion 34a, and is connected to a circuit pattern (not shown) formed on an upper surface of the flat plate portion 34a. The through hole 31d formed in the housing 31 and the through holes 34b formed in the flat plate portion 34a are opposed to each other and the opposite end portion 33d of the central conductor 33b of the probe 33 is inserted through the hole 34c formed in the flat plate portion 34a. In this state the circuit board 34 of the above configuration placed on the bottom wall 31a of the housing 31 and is fixed by a suitable means. The opposite end portion 33d of the central conductor 33b projected above the circuit board 34 is soldered to a circuit pattern by solder 37.
As shown in FIG. 14, a short-circuit wall 38 is formed in a box shape using a metal such as die-cast aluminum or zinc and is secured to the circuit board 34 by a desired means, e.g., caulking, so as to cover the through holes 34b formed in the circuit board. A bottom portion 38a of the short-circuit wall 38 functions as a short-circuit portion for the probe 36.
A cover 39, which is constituted by a single rectangular metallic plate (see FIGS. 13 and 14), is placed on the stepped portions 31e (see FIG. 15) of the side walls 31b of the housing 31 and is fixed by a suitable means. The receptacle portion 31c (see FIG. 14) of the housing 31 is hermetically sealed and the interior thereof is shielded electrically.
In the conventional converter for satellite broadcast reception, however, since the waveguide 32 and the holding portion 32d are formed integrally by die-casting aluminum for example, the material cost is high and it takes a considerable time for the manufacture, that is, the productivity is poor.
Besides, since the holding portion 32d is formed (see FIG. 15), the mold used for die casting is complicated and expensive, thus giving rise to the problem that the converter becomes expensive.
Further, it is necessary that the insulating portion 33a of the probe 33 be press-fitted into the holding portion 32d of the waveguide 32; besides, the press-fitting work is performed in the hollow portion 32c which is narrow. Consequently, a considerable time is required for the manufacture, that is, the productivity is poor.
It is an object of the present invention to provide a converter for satellite broadcast reception which is superior in productivity and inexpensive.
According to the first means adopted by the present invention for solving the above-mentioned problems there is provided a converter for satellite broadcast reception, comprising a box-shaped metallic housing, a cylindrical waveguide, and a probe attached to the waveguide, the probe having a cylindrical insulating portion and a central conductor piercing through a central part of the insulating portion, the waveguide being formed by bending a metallic plate and being integrally provided with a holding portion positioned outside the waveguide to hold the insulating portion of the probe.
According to the second solving means adopted by the invention, the insulating portion of the probe is held grippingly by both an outer surface of the waveguide and the holding portion.
According to the third solving means adopted by the invention, the holding portion is provided with a retaining piece for locking a free end side of the holding portion to the waveguide.
According to the fourth solving means adopted by the invention, the holding portion covers the probe throughout the whole in the longitudinal direction of the insulating portion which is exposed from the waveguide.
According to the fifth solving means adopted by the invention, the holding portion covers the probe throughout the whole in the longitudinal direction of the central conductor which is exposed from the waveguide.
According to the sixth solving means adopted by the invention, the insulating portion with the central conductor installed therein is formed with a slot in the longitudinal direction thereof, and one end portion of the central conductor is bent along the slot.
According to the seventh solving means adopted by the invention, an outer surface of the insulating portion of the probe includes a flat surface, and the probe is held by the holding portion in an abutted state of the flat surface against an outer surface of the waveguide.
According to the eighth solving means adopted by the invention, the flat surface formed as a part of the outer surface of the insulating portion is perpendicular to an extending direction of one end of the central conductor, and the probe is held by the holding portion in an abutted state of the flat surface against the outer surface of the waveguide.
According to the ninth solving means adopted by the invention, an insertion hole for insertion therein of the central conductor is formed in the waveguide, and with the central conductor inserted into the insertion hole, the insulating portion of the probe is placed on the outer surface of the waveguide so as to straddle the insertion hole.